This invention deals generally with separating material entering wells and more specifically with a multiple well pumping system which is automatically responsive to the flow into and the liquid level within the well.
Many installations for the removal of contaminants from ground water use one or more wells. Many such systems pump water up to the surface separately in order to create a "cone of depression" in the region so that contaminants dissolved in ground water, those which float atop the ground water and those which sink in ground water can be collected. However, most systems, even those systems which do not separately pump out the contaminants, must pump out considerable quantities of contaminated ground water to purify it.
Such multiple well systems have several features in common. If they use multiple pumps, the systems are usually quite complex and expensive because each pump in each well requires separate controls. If, on the other hand, a system uses a single pump for multiple wells, it is likely that the pumping action of each well will be affected by all the other wells.
For instance, one type of multiple well system uses a single vacuum pump connected to a manifold from which pipes are run to several wells. Such multiple well system have severe operational problems because all the wells can stop operating if the level of liquid in any one well drops below the location of the well pipe intake. Under such circumstances, the well without liquid at the intake sucks in air and the vacuum in all the other wells fails, so all pumping stops. The conventional manner in which this failure is prevented is to constantly adjust the flow from each well to match the flow into the well in order to keep the liquid levels in all the wells above the intakes. Such action requires complex controls and/or constant surveillance of the equipment by experienced personnel, since the flow into any well can change unpredictably.
Other multiple well systems use individual pumps within every well, but both the electric submersible pumps and the pneumatic pumps typically used for this purpose are costly because multiple pumps are required, and they have limitations in regard to their difficulty in handling low flow rates. The pneumatic systems are limited due to the requirement of the drive compressors to operate at a minimum duty cycle, that is, to operate a certain minimum portion of each time period. Thus, there is a low flow limit for the wells below which there is not sufficient operation of the compressors.
Electric submersible pumps have similar low flow limits, and they also require individual motor starters for each pump. They also have another limitation which adds significantly to the cost of their use. The conventional manner in which the liquid level in a well is controlled is by locating sensors, usually conductivity probes or float switches, within the well so that the sensors turn the pump on and off. However, since wells used for the removal of contaminants must be assumed to have volatile vapors present, for electric pumps all such controls in the wells must be explosion proof. This not only adds to the cost of the initial installation but also to the maintenance of such systems.